An in-wheel motor is disposed in the inside of a wheel. Accordingly, unlike an engine (internal combustion engine), it is unnecessary to mount the in-wheel motor on a vehicle body of the automobile and hence, the in-wheel motor is advantageous with respect to several points including a point that the vehicle can ensure a large inner space in the vehicle body. As a suspension device for mounting the in-wheel motor on a lower side of the vehicle body, conventionally, for example, there have been known a suspension device described in JP-A-2004-090822 (patent literature 1) and a suspension device described in JP-A-2006-240430 (patent literature 2). Patent literature 1 describes the configuration where an in-wheel motor is suspended by a double wishbone type suspension device or a strut type suspension device. Patent literature 2 describes the configuration where an in-wheel motor is suspended by a strut type suspension device.
FIG. 11 shows the connection structure between the in-wheel motor and the suspension device described in patent literature 1. The conventional in-wheel motor 201 includes: a circular cylindrical body 201b having a thickness in an axis O direction; and a motor 202 and a wheel support portion 203 projecting from the body 201b. The in-wheel motor 201 is disposed in an in-wheel empty region defined by a rim 205 of a wheel 204, and is coaxially joined to a wheel body of the wheel 204 by bolts 206 on one side in the axis O direction. On the other hand, the in-wheel motor 201 has the motor 202 and the wheel support portion 203 on the other side in the axis O direction. An upper end of the wheel support portion 203 is connected to an upper suspension member 208 at a connection point 207, and a lower end of the wheel support portion 203 is connected to a lower suspension member 210 at a connection point 209. The respective connection points 207, 209 are also referred to as hard points, and form ball joints. A straight line which passes the connection points 207, 209 constitutes a steering axis K. The in-wheel motor 201 and the wheel 204 are steered to a rightward direction or a leftward direction about the steering axis K.